DURING a recent hydrographical cruise of the Atlantis, the oxygen consumption in samples of water taken from eighteen levels between surface and 4,600 metres depth at Station 2886 (32° 19 N., 65° 59 W. ; June 19, 1937) was determined under controlled laboratory conditions. Two glass bottles (with ground-glass stoppers) were filled from each of the Nansen water bottles as soon as they were brought on deck ; one set of eighteen samples was stored at a temperature of 11° in an electric refrigerator and the other set at a temperature of 24° in the laboratory. After ten days of storage in darkness, oxygen contents of the two sets of samples were determined and subtractions of these values from initial oxygen contents of the samples gave results we have termed oxygen consumption.